Various organs of the gastrointestinal tract such as the stomach, small intestine and colon contain cells that are believed to govern the organs' periodic contractile behavior. In healthy humans, in certain regions of the organs, these cells generate and propagate rhythmic electrical signals. In general, several types of electrical potential activities have been observed in the gastrointestinal tract. Consistent slow wave or pacesetter potentials have been observed and higher frequency spike activity has been observed. The pacesetter potentials are continuously propagating, relatively low frequency, cyclic depolarizations of the smooth muscle cell lining. The higher frequency spike bursts generally correspond with smooth muscle contractile activity and peristalsis. In general, when the spike burst activity occurs, it appears to be at a fixed time delay with respect to the slow wave potentials. It is believed that when the pacesetter potentials are combined with a chemical or neural excitation of the cells, smooth muscle contractile activity occurs. Also it is believed that the pacesetter potentials control and coordinate the frequency and direction of the contractions.
Electrical stimulation of the gastrointestinal tract has been proposed to treat motility related disorders and other gastrointestinal diseases or conditions. The electrical stimulation has been proposed in a number of forms, such as, e.g., pacing, electrical contractile stimulation or other stimulation, e.g., to treat nausea or obesity. Electrical pacing of the gastrointestinal tract is generally defined as a periodic electrical stimulation that captures and/or controls the frequency of the pacesetter potential or slow wave activity of the gastrointestinal organ (including in a retrograde direction). Electrical contractile stimulation generally refers to stimulation that directly causes or results in muscular contraction associated with the gastrointestinal tract. In some disease states, dysrhythmias of the gastric pacesetter potentials may be present. The result of the abnormal pacesetter potentials may be gastric retention of food. Electrical stimulation of gastric tissue has been proposed to induce peristalsis. Electrical stimulation has also been proposed to treat obesity by altering gastric motility, or by stimulating neural pathways. For example, one treatment method causes the stomach to retain food for a greater duration. Electrical stimulation has also been proposed to slow the gastric emptying to treat a disorder known as dumping syndrome where the stomach empties at an abnormally high rate into the small intestine causing various gastrointestinal disorders. In particular, electrical pacing of gastric pacesetter potentials has been proposed to induce regular rhythms for the pacesetter potentials with the intent of inducing regular or controlled gastric contractions.
Within the stomach, at least one pacemaker region has been identified near the interface of the fundus and the corpus along the greater curvature. This region has been one target for gastric pacing. Peristalsis controlled by this region is believed to serve to mix and break down food and propel small particles through the pylorus into the duodenum. It is believed that gastric emptying of liquids is controlled by the fundus. This region is believed to create with characteristic contractions, a pressure gradient between the fundus, pylorus and duodenum that relates to the rate of gastric emptying.
An early attempt at a gastric stimulation device included an electrode at the end of a nasogastric tube or catheter. The nasogastric tube was passed into the stomach transnasally. Electrical stimulation was applied through the electrode on the end of the tube using an external stimulator unit. The return electrode was placed on the abdomen. This device required a transnasal procedure whenever stimulation was required. It would therefore be desirable to provide a device that could reside in the stomach for a long-term treatment protocol.
Other devices used to pace the stomach have generally been implanted by accessing the outside of the stomach through an opening in the abdomen, either through open surgery or laparoscopic surgery. Electrodes have been attached to the stomach wall with attached leads extending through the abdomen.
These procedures involve implanting a pacemaker device in a subcutaneous or sub-muscular pocket. The devices are anchored into the subcutaneous or sub-muscular pocket initially by a suture anchor and eventually by fibrous tissue ingrowth around the unit. The pacemaker device housing is typically constructed of a titanium or stainless steel material with connectors molded into an epoxy header. The devices are thin in one dimension so that they are less visible when implanted directly under the skin or muscle layer. Therefore, in order to accommodate the necessary battery capacity, the devices are widely shaped, e.g. round or kidney shaped in the other two dimensions. The leads extend from the unit's epoxy header to a stimulation site remote from the pacemaker unit.
A gastrointestinal pacemaker having phased multi-point stimulation has been proposed with electrodes placed in multiple points around the GI tract including on the inner or outer surface of the stomach. As described, the device could be preprogrammed or include an implantable pacemaker detachably coupled to the multiple electrodes in their various locations, and including an electronic controller that may be programmed by using an external programmer to set stimulation parameters. The implantable pacemaker is located remote from the stimulation sites.
Some gastric stimulation procedures have proposed electrical stimulation in response to sensing electrical pulses within the stomach within a particular range. Additionally, a device has been proposed to sense electrical parameters to determine the fullness of an organ and the absence of muscular contraction, and to deliver electrical muscular contraction stimulation to the organ in response.
In general, the currently proposed gastric electrical stimulation procedures are relatively invasive and require accessing the stomach through the abdomen, e.g., in an open or a laparoscopic procedure. The units have relatively wide dimensions in one plane. Accordingly, it would be desirable to provide a less invasive procedure and device for electrically stimulating the stomach. It would also be desirable to provide a device in which various components are accessible for removal or replacement, particularly in a less invasive procedure.
A machine that places a nylon tag has been proposed for attaching a “payload” to the inner wall of a stomach. The machine places the tag through the stomach wall and back into the stomach in a manner that causes folding of the stomach wall and may cause tissue damage when the smooth muscle of the stomach wall contracts. It would therefore be desirable to provide a means and method for implanting, a functional device having therapeutic or diagnostic functions, within the stomach wall, so that the stomach wall is protected from damage from mechanical stresses and forces due to the attachment of the stimulator device. It would further be desirable to employ such device and method that at the same time protect the functional device from the stomach's corrosive environment, or churning or grinding forces, and peristaltic movement, typical when food is digested and passed out of the stomach into the intestinal tract.